1. Field of the Invention
The present invention relates to the art of large pipe fabrication. More particularly, the present invention relates to the structural fabrication of a coaxial flow mixing joint.
2. Prior Art
There are countless process and flow conditions in industry that require the blending of two or more fluid flow streams. Unless on of the flow streams is particularly turbulent and the two streams are of substantially the same density, a simple T-junction will not accomplish immediate blending. The injected flow stream will merely stratify within the mixed stream pipe.
For ideal mixing, an injected flow stream should be released coaxially of the main flow stream. In other words, the injected flow stream conduit should penetrate the main flow stream conduit wall and internally align concentrically and coaxially with the main flow conduit.
Although this principle is well understood, physical fabrication of such a pipe joint is intricate. Penetration of the main flow pipe wall by the injected flow pipe constitutes a flow stream disruption in the main flow channel. Moreover, the disruption may represent a significant flow area reduction causing changes in the main flow stream direction and velocity. These changes cause dynamic eddys, stagnation zones and periodic force and flow gradients around the injected flow pipe. The result is vibration and structural stress. Such vibration and stress eventually fatigues and breaks the welds holding the pipe assembly together.
When the main flow stream is a mixture or suspension such as an aqueous slurry of cellulose fiber and water, fiber flocs and lumps can form in the stagnation zone on the downstream side of the injected flow pipe which are periodically returned to the main flow stream to be ultimately found as blemishes in a finished paper web.
Responsive to these known difficulties arising from concentric injection flow pipe junctions, prior art practice has attempted several solutions. To structurally reinforce the concentrically suspended, interior portion of the injected flow pipe, struts or webs have been welded between the outer surface of the interior pipe and the inner surface of the exterior or main flow pipe. This procedure is possible only in those cases where the interior of the main flow pipe is acccessible to the welder. Furthermore, struts and/or webs in this position tend to aggravate dynamic flow disturbances started by the injected flow pipe penetration.
To fair the flow stream around the injected flow pipe, fillets have been constructed of polyester and epoxy resin to fill the stagnation volume behind (downstream of) the injected flow pipe penetration zone and along the concentrically located leg of the injected flow pipe. This procedure also requires manual access to the main flow pipe interior. Additionally, the composite fillet is susceptible to fracture and crumbling from which free moving particles are removed and carried downstream into pumps valves and other flow control equipment.
It is, therefore, an object of the present invention to provide a fabrication technique for concentric, injection flow, pipe junctions that fair the flow stream around the injected flow pipe with securely welded or bonded structural partitions.
Another object of the present invention is to provide adequate structural reinforcement for the concentrically located, interior leg of the injected flow pipe element of a concentric injection flow pipe junction.
Another object of the present invention is to provide an assembly and fabrication technique for a concentric injection flow pipe junction by which all joints and seams are externally accessible for quality welding or bonding.